Remove unnecessary square brackets.

src/@dseries/chain_.m

src/@dseries/exist.m

src/@dseries/hdiff_.m

src/@dseries/hpcycle.m

src/@dseries/hpcycle_.m

src/@dseries/hptrend.m

src/@dseries/hptrend_.m

src/@dseries/insert.m

src/@dseries/onesidedhpcycle.m

src/@dseries/onesidedhptrend.m

src/@dseries/onesidedhptrend_.m

src/@dseries/save.m

src/@dseries/set_names.m

src/@dseries/ydiff.m

src/@dseries/ydiff_.m

src/initialize_dseries_class.m